Flat type parts of different sizes generally need to be duplicated or reverse engineered for a multitude of reasons. For example, gaskets on antique type automobiles may not be easily available and thus would need to be reduplicated. A gasket on an internal combustion engine can generally include a flat metal type part shape having unique side edges and unique through-holes for fasteners, manifold openings, and the like.
In addition to duplication purposes, the inspecting of flat shaped parts such as metal parts, in order to verify tolerance compliance to specific dimensional limits, requires high degrees of accuracy.
Precise part measurements of the parts can then be then be placed into known laser burning machines to produce the parts. Several types of techniques have been known over the years to measure parts but are known to be problematic.
Part measurements and inspections have included the use of CCD (charge coupled devices) arrays and cameras. See for example, U.S. Pat. No. 4,711,579 to Wilkson; U.S. Pat. No. 5,184,217 to Doering; U.S. Pat. No. 5,319,442 to Rosser; U.S. Pat. No. 5,351,078 to Lemelson and U.S. Pat. No. 5,636,031 to Passoni. However, the use of these elaborate sensor arrays and cameras require multitudes of components and equipment, and extensive construction and operation that can all be expensive, time consuming, and not be able to provide accurate precise measurements of the parts.
Other types of approaches have included the use of laser systems. See for example, U.S. Pat. No. 6,011,255 to Rueb; and U.S. Pat. No. 6,066,845 to Rueb et al. (the Virtek Vision Corporation patents). In these types of systems, a laser beam probe scanning system moves a single small diameter collimated beam from a fixed position scanner located five feet above and centered on a 4 by 4 foot square glass datum. The beam scans the part at high speed, steered by two galvanometer mirrors, tracking the part""s edge by keeping the beam half on and half off it""s edge. The half off the edge portion of the beam is reflected back to the scanner by a flat high resolution, vinyl retro reflector, mounted below the datum glass, off each galvo mirror, off a beam splitter mirror to a photo diode detector. In these types of systems angular distortion is a major problem in this design (the only true reading would be when the beam is perpendicular to the datum). For instance, all round holes scanned with the beam at an angle are seen as ovals, it""s narrow dimension is shortened additionally because the beam can only measure the top near side and far side bottom of the hole, which precludes measuring the hole""s width. All this distortion gets greater as the angle of the beam to the datum gets greater when scanning features at greater angles on larger and larger parts. It also gets greater as the part gets thicker. This distortion is corrected in software, based on the thickness of the part and the angle of the scan beam to the datum at the instant any feature is measured. There can be other types of problems with these systems as listed below with other laser systems.
Additional types of laser type systems have also been disclosed. See for example, U.S. Pat. No. 5,291,270 to Koch; U.S. Pat. No. 5,403,140 to Carmichael et al.; and U.S. Pat. No. 5,504,345 to Bartunek et al. However, the laser systems known to the inventors also have problems. For example, these systems generally require the part be placed in an exact location for measurement purposes, where having the part off position can provide erroneous measurements. In addition, these systems generally rely on reflection and/or backscattering of the signal where many distance measurements must be calculated which can also result in erroneous measurements. Furthermore, another general problem with these systems is that the radiating signals can over-run the sides of the object being scanned, and can require the measurements having to be restarted from scratch resulting in extra time and cost for the measurements.
In addition to the above patents, businesses have also tried to inspect parts. One of the subject inventors, Don Macaulay, was the principal engineer in developing high speed optoelectronic parts flaw inspection and dimensional inspection machinery for RCA Industrial Automation Systems, Plymouth, Mich. between February 1966 and August 1969, and for Sensors Inc. of Ann Arbor, Mich. between October 1970 and May 1972. The machinery included linear arrays of photo diodes and HeNe laser sources that were no better than the prior art of record described above, in that these devices were incapable of accurately and easily and economically detecting exterior side edges opening locations and side edges of the openings in parts that needed to be duplicated and/or inspected. Thus, the need exists for solutions to the above stated problems.
The first objective of the present invention is to provide a system for inspecting and measuring parts by placing a part in a stationary non specific position adjacent a scanning signal.
The second objective of the present invention is to provide a system for inspecting and measuring parts that allows the parts to be quickly and easily scanned and measured.
The third objective of the present invention is to provide a system for inspecting and measuring parts that allows for easy reverse engineering of the part.
The fourth objective of the present invention is to provide a system for allowing parts to be continuously inspected and measured without having to restart the measurements of the parts.
The fifth objective of the present invention is to provide a system for inspecting and measuring parts with a look ahead signal for allowing only the part to be measured.
The sixth objective of the present invention is to provide a system for inspecting and measuring parts by eliminating any angular distortion that would need to be corrected. The invention always scans the part with the beam or beams perpendicular to the datum.
The seventh objective of the present invention is to provide a system for inspecting and measuring parts having a resolution at least 50 times greater than an angular scan system.
The eighth objective of the present invention is to provide a system for inspecting and measuring parts having an improved signal to noise ratio. The invention does not use a beam splitter mirror as used in an angle scan system does which can lose 75% of it""s beam strength.
The ninth objective of the present invention is to provide a system for inspecting and measuring parts that does not require a retro-reflector (exact losses unknown) but quite high due to scattered return beam light reflected at angles which cannot return to the scanner optics.
The tenth objective of the present invention is to provide a system for inspecting and measuring parts using a scan circle that provides a constant beam circular scan velocity.
The eleventh objective of the present invention is to provide a system for inspecting and measuring parts that uses a small diameter collimated scan beam which provides higher resolution measurements (the resolution of measurement being inverse to scan beam to diameter).
The twelfth objective of the present invention is to provide a system for inspecting and measuring parts that uses a cylindrical shaped scan circle that provides precise geometric type measurements of edge and through-hole diameters.
The thirteenth objective of the present invention is to provide a system for inspecting and measuring parts using a scan beam""s rotation at high speed in a small diameter circle to make 133 measurements per second of the part""s edge or features at approximately 0.00004 to approximately 0.00015 inch resolution. While for XY motion system""s servo tracking purposes, the scan circle is treated as a spot 10 to 40 times the diameter of it""s scan beam diameter. This allows for much greater XY axis scanner tracking speeds than would be possible if the system had to keep only it""s very small scan beam tracking the part""s edge.
A system and method for optically measuring and inspecting parts is described. The system and method can include a support surface having a transparent portion for supporting a part thereon. An optical beam generator such as a laser generates a collimated laser beam along a perimeter side edge of the part. A detector such as a photo diode, on the opposite side of the support surface detects the portion of the laser beam not stopped by the part""s edge. An XY motion stage that can be located below the support surface can be moved by a servo type motor which moves the optical beam generator and the detector above the support surface in unison about the perimeter edges of the part. A computer can receive the detected optical beam and provide x and y coordinates of the perimeter edges of the part. Next, the XY motion stage can be used to scan a surface portion of the part with the optical beam and the detector moving in unison, and locate x and y coordinates for openings in the part. Finally, the XY motion stage can move the optical beam and the detector in unison about perimeter edges of the openings in the part, and provide x and y coordinates of the perimeter edges of the openings in the part.
The optical beam can include two beams one beam for tracing the edges of the part, finding the openings in the part, and tracing the edges of the openings, and a second beam for continuously and consistently keeping portions of the first beam on the part. Separate photo diodes can be used for each of the beams
The two beams can include an outer rotating look ahead beam, and an inner rotating scan beam concentric to the outer beam. Both beams rotate at the same rpm and move at a constant speed across the part""s edges and surface. Both beams can decelerate down to a full stop with their common center on one of: a corner of the perimeter edges of the part, an edge of the surface of the part, and a corner of interior edges of the openings of the part. A working example has both beams rotating at approximately 4000 rpm, and moving at approximately 5 inches per second. A working example of the inner beam has a beam diameter of approximately 0.005 to approximately 0.02 inches, rotating in a circle approximately 05 to approximately 0.2 inches (adjustable ) in diameter. The working example further has the outer beam approximately 0.20 inches in diameter, rotating in a circle approximately 3 inches in diameter. Beam rotational speed and scanner moving speeds can be changed using keyboard commands. Non adjustable beam diameters and scan circle diameters, can be changed using optional quick change scanner heads.
Further objects and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment which is illustrated schematically in the accompanying drawings.